The present invention relates to a filament winding apparatus and a yarn end processing method. More particularly, this invention relates to a yarn end process that temporarily fixes the winding-start end of a yarn to be wound around a mandrel and cuts the yarn at a predetermined length with the winding-finishing end of the yarn secured to the mandrel.
A filament winding method efficiently produces FRP (Fiber Reinforced Plastic) pipes or containers. The filament winding method generally uses an apparatus that has a chuck mechanism for holding a portion of a shaft protruding from both ends of the body of a mandrel and rotating the mandrel at a predetermined velocity. A filament feeding mechanism is used to wind a filament (yarn) impregnated with resin around the body of the mandrel. The filament winding apparatus normally requires that the winding-start end and winding-finishing end of a filament be secured manually to the mandrel at a predetermined position. For example, the winding-start end of a filament is securely tied to a pin protruding from the shaft portion or body of the mandrel or the winding-finishing end is secured to the mandrel with adhesive tape.
Japanese Unexamined Patent Publication (KOKAI) No. Hei 7-69539 discloses an apparatus that automatically secures the winding-start end and winding-finishing end of a wire to a mandrel at a predetermined position. This apparatus feeds the winding-start end of a wire to a predetermined position of the mandrel by a wire feeding mechanism and fixes that end to the mandrel using a wire holding device. When winding of the wire on the body of the mandrel is finished, the winding-finishing end of the wire is secured to the body of the mandrel with adhesive tape by an adhesive-tape adhering mechanism.
Because the apparatus disclosed in Japanese Unexamined Patent Publication (KOKAI) No. Hei 7-69539 fixes the winding-start end and the winding-finishing end with different mechanisms, the apparatus is complex and costly. The adhesive tape that is used to fix the winding-finishing end to the mandrel may remain as foreign matter in the final product. This reduces the quality of the product. The use of adhesive tape is inadequate, particularly in the case when the final product is manufactured by winding a high-performance filament (e.g., a carbon fiber) impregnated with a resin around a mandrel and hardening the filament.
The holding device that holds the winding-start end of the filament uses one end face of the mandrel so that the wire is held between the end face of the mandrel and a pressing ring when securing the mandrel to a chuck. This raises a problem that the machine must be stopped when using plural layers of filaments on a mandrel, when using different types of wires (filaments) on a specific layer, when using plural wires on a middle layer, or when using plural wires from a middle of winding.
Accordingly, it is an object of the present invention to provide a filament winding apparatus and a yarn end processing method in which the winding-start end and winding-finishing end of a filament are fixed to a mandrel or a yarn winding member with the same mechanism, without the possibility of leaving foreign matter such as adhesive tape in the final product.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a yarn end processing method is provided for a filament winding apparatus for winding a yarn around a surface of a mandrel or a yarn winding member. The yarn is wound with a guide member, which moves back and forth in the axial direction of the mandrel or the yarn winding member, while the mandrel or the yarn winding member is supported and rotated. The method comprises:
initiating yarn winding with an end portion of the yarn held by a holding device provided in a relatively rotatable manner on a rotary shaft, which rotates while supporting the mandrel or the yarn winding member;
winding the yarn on the mandrel or the yarn winding member such that, even when a yarn extending from the mandrel or the yarn winding member to the holding device is cut, an end portion of the yarn wound around the mandrel or the yarn winding member will not unwind;
cutting the yarn extending between the mandrel or the yarn winding member and the holding device with a yarn cutting device and releasing the yarn by the holding device before that yarn winding is finished; and
performing end winding when winding of the yarn around the mandrel or the yarn winding member is finished;
holding the yarn with the holding section; and
cutting the yarn between the mandrel or the yarn winding member and the holding device with the yarn cutting device.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.